The focus of this application is to elucidate the functional role and regulation of TTF-1 in lung development. Aim 1 is to determine the role of TTF-1 in the regulation of lung morphogenesis by isolating and characterizing putative TTF-1 target genes. Aim 2 is to determine the role of TTF-1 in regulating differentiation-specific genes. Aim 3 is to identify higher order combinatorial protein-protein interactions as possible regulatory means for the cell type and tissue specificity of TTF-1 activity. Aim 4 is to determine the cis-and trans-acting factors which regulate TTF-1 during lung morphogenesis.